A mobile or cellular telephone is a well-known example of an apparatus according to the above. Within the context of this document reference will consistently be made to a mobile telephone for any commercially available mobile communications network, such as GSM. However, the invention is not limited to merely a mobile telephone; other equally applicable examples of electric apparatuses are radio pagers lap-top computers, organizers and communicators (also known as personal digital assistants), i.e. portable telephone devices including a computer and application programs, such as a built-in calendar, Moreover, the term “mobile communications network” is meant to have the widest possible meaning, thereby including all types of cellular networks, satellite networks, wireless local area networks (LANs), etc.
Mobile telephones are generally provided with a visual indicator for indicating status information about the connectivity of the mobile telephone with respect to the mobile communications network. Moreover, a battery charge indicator in often provided for alerting a user of the telephone, when the remaining battery charge drops below a predetermined limit. W098/56152 discloses a mobile telephone having such status indicators.
One common approach is to provide the mobile telephone with a combined green and red indicator window mounted at the top of the telephone housing. A dual-color light emitting device, such as a red light emitting diode (LED) combined with a green LED, is mounted to a printed circuit board within the telephone housing. An optical light guide is arranged between the external indicator window and the internal light emitting device. The dual-color light emitting device may for instance be used according to the following:
Green light flashing at lowThe mobile telephone is infrequencycontact with at least one basetransceiver station (BTS)No green lightNo contact with any BTSGreen light flashing at aA message is available (such ashigher frequencySMS)Red flashing lightLow battery charge levelRed continuous lightThe battery is being recharged
Consequently, a green visual indicator is used for informing the user of whether the mobile telephone is in operative contact with the mobile communications network (so that, inter alia, the user is free to initiate an outgoing telephone call), or whether the mobile telephone has currently lost its operative contact with the mobile communications network.
Many mobile telephones and other portable communication apparatuses are provided with at least one component, which either operates with, or is sensitive to, infrared (IR) or visible red light. For instance, the mobile telephone may be equipped with an IR port for performing information interchange with external devices. Another example is an optical detector, which is adapted to detect when the surrounding light is weaker than a predetermined limit, and in response turn on e.g. the display or the keyboard illumination, so as to give the user a better opportunity of operating the telephone also in situations of darkness. Such an optical detector may alternatively be used as a proximity switch for detecting whether the user or an external object is located in proximity with the mobile telephone. Yet another example is various unprotected integrated circuits (ICs) or other semiconductor components, which have no protective coating and which may be damaged if exposed to infrared light.